The present disclosure relates to an electric storage device constituted by secondary batteries, for example, and an electronic device, a power system, and an electric vehicle that use the electric storage device.
The electric storage device including batteries such as lithium ion secondary batteries is widely used as a mobile electronic device, an electric vehicle, a backup power source, etc. Regarding the electric storage device, there are problems that imitations by parties other than regular manufacturers are distributed or illegal modification is performed. It is possible that such imitations or illegally modified products (hereinafter, generally referred to as irregular products) use an inferior batter element, or have defects in protection circuit parts or a circuit. As a result, the irregular products often have a problem in terms of safety as compared with regular battery packs. Therefore, as described in Patent Literature 1, it is proposed that an IC (Integrated Circuit) for authentication is mounted on each of the electric storage device and the electronic device and, only when mutual authentication is established, the electric storage device is determined to be regular and used.
In the conventional method of determining whether the electric storage device is regular by authentication, it is necessary to mount an IC for authentication on both the electric storage device and the electronic device and provide a terminal for communication to both of them, and there is a problem of causing increase in cost. Moreover, there is a problem that modified products in which an IC for authentication is reused cannot be detected.
Furthermore, the following Patent Literature 2 describes that the internal resistance of battery cells of a battery pack is measured and it is determined, when the internal resistance is smaller than previous internal resistance, that the battery cell has been exchanged. That is, in the case of a lithium ion secondary cell, the internal resistance is normally increased as a use period passes, and thus it is determined that a battery cell has been exchanged when the internal resistance is decreased.